Window assemblies which are pre-assembled prior to installation are widely used, particularly for motor vehicle applications. Pre-assembly of the glazing unit for simple insertion into a window opening in the vehicle body during vehicle assembly has been found to yield substantial cost and quality advantages. Such window assemblies typically include a metal or plastic frame holding one or more glass or plastic panes. The frame may be formed in place around the perimeter of the transparent panes, producing so-called encapsulated window assemblies. Encapsulation in this way is not always suitable, however, for window assemblies having a moveable pane. A sliding vent window is shown in U.S. Pat. No. 4,502,248 to Thomas Jr. et al, having a molded plastic guide bonded to one peripheral edge of the glass. The guide travels within a channel in a pillar supported by the vehicle body. This construction does not, however, permit a true pre-assembly of the glazing unit prior to installation in the motor vehicle window opening.
Window assemblies also are known having fixed or slidable panes attached to a pre-constructed base or frame. Considerable complexity generally is involved in design and assembly of such glazing units to obtain reliable component functioning (such as noise and weather sealing, smooth sliding, etc.), durability and accurate and consistent control of component positioning.
Improved window assemblies with slidable panes are needed particularly for motor vehicles, which can be pre-assembled prior to installation in the window opening. It is an object of the present invention to provide such window assemblies having a slidable pane, optionally being integrated with one or more fixed panes, which are readily pre-assembled and are suitable for meeting strict fit and finish requirements prevalent in motor vehicle and architectural glazing applications. These and other objects and advantages will be apparent from the following disclosure of the invention and description of various alternative embodiments.